Exercise, nutrition counteract bone loss during spaceflight

Abstract

MedWire News: Astronauts can counteract the bone loss typically associated with spaceflight through a combination of improved nutrition and resistance exercise, NASA scientists have shown.

In the past 4 decades, astronauts have tried various measures to counteract the microgravity-induced bone loss that occurs during long-duration spaceflight.

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One approach, known as the "interim Resistive Exercise Device" (iRED), allows astronauts to perform both aerobic exercise (using treadmill and cycle) and muscular endurance (using elastic expanders). However, it does not offer additional protection against bone loss as compared with aerobic exercise alone.

In 2008 a new device was developed, the Advanced Resistive Exercise Device (ARED), which is more "robust" than the iRED and with greater resistance capability - a maximum load of 270 kg as opposed to 135 kg with the iRED.

"The ARED allows performance of a much greater variety of exercises," explain Scott Smith (NASA Johnson Space Center, Houston, Texas, USA) and co-authors writing in the Journal of Bone and Mineral Research.

For their study, Smith et al analyzed diet, bone, and biochemical data for 13 crew members on missions to the International Space Station. The missions lasted 5.33 months, on average; the first eight astronauts used the iRED while the last five used the ARED.

Results showed that markers of bone resorption and bone formation increased in all astronauts toward the end of the mission and continued to increase after landing.

Of note, bone mineral density (BMD) was unchanged in the ARED astronauts at the end of the mission as compared with preflight; this group also returned from the mission with a higher percentage lean mass and lower percentage fat mass.

Overall body mass was unchanged after flight with both devices, and all crew members had normal vitamin D status both before and during flight.

"These data document that resistance exercise, coupled with adequate energy intake and vitamin D, can maintain bone in most regions during 4- to 6-month missions in microgravity," Smith et al conclude. "This is the first evidence that improving nutrition and resistance exercise during spaceflight can attenuate the expected BMD deficits previously observed after prolonged missions."